Atactic polypropylene is a non-crystalline, naturally occurring by-product from the manufacture of the elastomer roofing material polypropylene. More recently, atactic polypropylene has been manufactured using atactic copolymers of ethylene and propylene. These forms are known as atactic poly alpha olefins and can be made "adhesive grade" with the addition of polybutene. Adhesive grade atactic poly alpha olefins have broad usage in the adhesive industry.
Atactic polypropylene, a natural adhesive, is sufficiently tacky at room temperature so as to stick to itself and most other objects. This characteristic makes the material extremely difficult to handle and store in a usable form. Additionally, atactic polypropylene is self-insulating, thus requiring large, complicated and expensive facilities and equipment to maintain large volumes of the material in a molten state.
Prior methods of handling and storing this material have met with dismal success. Efforts to package the material in relatively small cardboard containers are expensive, complicated and involve the removal of the container from the atactic polypropylene before use. Additionally, methods of handling and storing the material in the form of thin slabs do not eliminate the problems associated with the natural tackiness of the material. The slabs still stick to each other and to other objects they contact. Finally, co-extruding the material within a polyethylene sheath and cutting it into small segments is expensive and must be done at a relatively high temperature. Additionally, the cut ends of the segments leave the material exposed, presenting the traditional problems associated with the natural tackiness of the material.
Furthermore, traditional methods of packaging and/or storing materials of extreme tackiness incorporating methods of cutting or shearing the materials are limited when applied to atactic polypropylene olefins since atactic polypropylene olefins smear at form-retention temperatures.
Finally, none of the above-referenced methods are improved by operation at a reduced temperature. Atactic polypropylene olefins have a very flat temperature to viscosity relationship, making even large changes in temperature result in relatively small increases in viscosity. Consequently, operation of these previously discussed methods are uneconomical at the temperatures needed to solve the viscosity-related problems with packaging and storing the materials.
Thus a need has arisen for a method and device for packaging and/or storing atactic polypropylene or other amorphous poly alpha olefins truly providing a simple, inexpensive and effective solution to the aforementioned problems and obstacles.